In spite of the extensive antiinflammatory research in the past two decades there is still an obvious need for an effective and well-tolerated agent for the treatment of rheumatoid arthritis. Conventional antiinflammatory-analgesic-antipyretic agents, such as aspirin, and many experimental new drugs under clinical evaluation, are mostly effective in providing symptomatic relief of the acute syndrome only. As a consequence, the antirheumatic actions of two other remedies, gold and particularly D-penicillamine, have received renewed interest in the past few years. The clinical efficiancy of both drugs has been confirmed by well-controlled multi-center clinical studies. Impressed by these findings, a growing population of rheumatologists have expressed the opinion that compounds possessing properties similar to D-penicillamine should be a valuable contribution to medicine in this important field. Thus it is an important discovery that acyl cyanoguanidines possess immunological properties similar to that of D-penicillamine, being of value in the treatment of rheumatoid arthritis and related inflammatory disorders, as well as antiinflammatory properties.